DESCRIPTION: (Applicant's Description) Prostate cancer's etiologies are still relatively unknown despite prostate cancer being the most common cancer among men in the United States. The incidence rate of prostate cancer in the United States has increased by more than 200 percent from 1990 to 1997 and prostate cancer mortality has increased by 39 percent during that same time period. As the number of estimated new cases and deaths for prostate cancer continue to rise, discerning what the causative factors are of this type of cancer is important. While not uncovering new hypotheses, meta-analyses conducted on previous studies evaluating associations between potential risk factors and prostate cancer may help to guide the search for the etiologies of this disease. Before deciding how to proceed with a case-control study measuring the complex association between prostate cancer and sexual history, we need to have a better understanding of the current information on sexual histories and possible confounders of the association. The various techniques suggested by researchers for meta-analysis can be generally summarized into two approaches: combination of significance levels and combination of effect sizes. In this study, we plan to look at a variation on combining effect sizes by combining of relative risk estimates. The overall aims of this proposal are to conduct research relevant to prostate cancer etiology by combining relative risk estimates (RRs) and their variances from previously conducted studies to examine both the strengths and consistency of the observed associations. We will conduct a large meta-analyses of sexual activity associated with prostate cancer, and two smaller meta-analyses related to vasectomy and dietary fat. To meet these aims, we will conduct three meta-analyses by examining the association between prostate cancer and each of the following risk factors: 1) sexual activity, 2) vasectomy, and 3) dietary fat. The relationship between prostate cancer and these risk factors will each be examined separately by combining risk estimates from each study for an overall relative risk estimate along with combined estimates by study design (e.g., cohort, case control), and by method of data abstraction. When data is available, we will also examine associations by race in an attempt to better understand the increased risk of prostate cancer among African-American men. The long term goal of this project is to follow up the results with a large case-control study of prostate cancer etiologies.